1. Field of the Invention
The present invention generally relates to a display device provided in a small electronic appliance such as a multifuntion electronic calculator generally called scientific electronic calculator and a method of display, and more particularly, to a device and a method of displaying, on a display portion having only several rows for displaying numerals and symbols in the vertical direction, a mathematical expression which requires, when normally displayed, more rows than display rows of the display portion.
2. Description of the Related Art
A small electronic appliance such as a multifunction electronic calculator generally called scientific electronic calculator carrying out calculation of various mathematical expressions other than functional calculation includes a display portion narrow in the vertical direction which displays only approximately three rows of numerals and symbols. When a mathematical expression is to be entered and displayed on such a small display portion, either of the following methods is employed.
(a) A mathematical expression is entered, as ordinarily displayed, in the vertical direction irrespective of the size of a display screen. In this method, only a part of the entered mathematical expression within rows of the display screen is displayed.
(b) Input of a mathematical expression requiring more rows in the vertical direction than the display rows of the display screen is made invalid. In this method, the size of a mathematical expression which can be displayed and entered is limited only in the vertical direction.
In the above-described method of (b), since it is not possible to enter and display a mathematical expression in the vertical direction which cannot be positioned on the display screen, use of the display device is substantially limited. On the other hand, in the method of (a), when a mathematical expression requiring, when normally displayed, more rows in the vertical direction than the display rows of the display screen is entered and displayed, only a part of the mathematical expression is displayed on the display portion. Therefore, it is difficult to grasp the entire mathematical expression, and it is extremely difficult to carry out editing or the like of the mathematical expression, such as change or deletion of a numerical value of one element of the mathematical expression for correction.
In either method of (a) or (b), if a partial expression, such as a fraction, requiring a plurality of rows for display in the vertical direction exists in a mathematical expression as an independent numerical element, such as a numerator or a denominator of a fraction, or a bottom argument or a top argument of an integral, the vertical size of the entire numerical expression changes. As a result, it is necessary to carry out such complicated operations that a display position of a numerical value once entered and displayed is moved and changed in the up and down direction, an integral sign is made longer, or that grouping symbols are made larger. Furthermore, in the method of (a), it is necessary to store data indicating which part of the entire mathematical expression is displayed on the display portion. As a result, the arithmetic processing for calculating the display position of each element of the mathematical expression in the display screen becomes more complicated.